// System.IO.BufferedStream
// Updated to work with .NET Micro Framework
// Changes by:
//     Chris Taylor (taylorza) - 26/08/2012

// System.IO.BufferedStream
//
// Author:
//   Matt Kimball (matt@kimball.net)
//   Ville Palo <vi64pa@kolumbus.fi>
//
// Copyright (C) 2004 Novell (http://www.novell.com)
//

//
// Copyright (C) 2004 Novell, Inc (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

using System;
using System.IO;

namespace DotNetWarrior.NetMF.IO
{
    public sealed class BufferedStream : Stream
    {
        private readonly Stream m_stream;
        private bool disposed;
        private byte[] m_buffer;
        private int m_buffer_pos;
        private int m_buffer_read_ahead;
        private bool m_buffer_reading;

        public BufferedStream(Stream stream)
            : this(stream, 4096)
        {
        }

        public BufferedStream(Stream stream, int buffer_size)
        {
            if (stream == null)
                throw new ArgumentNullException("stream");
            // LAMESPEC: documented as < 0
            if (buffer_size <= 0)
                throw new ArgumentOutOfRangeException("buffer_size", "<= 0");
            if (!stream.CanRead && !stream.CanWrite)
            {
                throw new ObjectDisposedException("Cannot access a closed Stream.");
            }

            m_stream = stream;
            m_buffer = new byte[buffer_size];
        }

        public override bool CanRead
        {
            get { return m_stream.CanRead; }
        }

        public override bool CanWrite
        {
            get { return m_stream.CanWrite; }
        }

        public override bool CanSeek
        {
            get { return m_stream.CanSeek; }
        }

        public override long Length
        {
            get
            {
                Flush();
                return m_stream.Length;
            }
        }

        public override long Position
        {
            get
            {
                CheckObjectDisposedException();
                return m_stream.Position - m_buffer_read_ahead + m_buffer_pos;
            }

            set
            {
                if (value < Position && (Position - value <= m_buffer_pos) && m_buffer_reading)
                {
                    m_buffer_pos -= (int) (Position - value);
                }
                else if (value > Position && (value - Position < m_buffer_read_ahead - m_buffer_pos) && m_buffer_reading)
                {
                    m_buffer_pos += (int) (value - Position);
                }
                else
                {
                    Flush();
                    m_stream.Position = value;
                }
            }
        }

        public override void Close()
        {
            try
            {
                if (m_buffer != null)
                    Flush();
            }
            finally
            {
                m_stream.Close();
                m_buffer = null;
                disposed = true;
            }
        }

        public override void Flush()
        {
            CheckObjectDisposedException();

            if (m_buffer_reading)
            {
                if (CanSeek)
                    m_stream.Position = Position;
            }
            else if (m_buffer_pos > 0)
            {
                m_stream.Write(m_buffer, 0, m_buffer_pos);
            }

            m_buffer_read_ahead = 0;
            m_buffer_pos = 0;
        }

        public override long Seek(long offset, SeekOrigin origin)
        {
            CheckObjectDisposedException();
            if (!CanSeek)
            {
                throw new NotSupportedException("Non seekable stream.");
            }
            Flush();
            return m_stream.Seek(offset, origin);
        }

        public override void SetLength(long value)
        {
            CheckObjectDisposedException();

            if (value < 0)
                throw new ArgumentOutOfRangeException("value must be positive");

            if (!m_stream.CanWrite && !m_stream.CanSeek)
                throw new NotSupportedException("the stream cannot seek nor write.");

            if ((m_stream == null) || (!m_stream.CanRead && !m_stream.CanWrite))
                throw new IOException("the stream is not open");

            m_stream.SetLength(value);
            if (Position > value)
                Position = value;
        }

        public override int ReadByte()
        {
            CheckObjectDisposedException();

            var b = new byte[1];

            if (Read(b, 0, 1) == 1)
            {
                return b[0];
            }
            return -1;
        }

        public override void WriteByte(byte value)
        {
            CheckObjectDisposedException();
            var b = new byte[1];

            b[0] = value;
            Write(b, 0, 1);
        }

        public override int Read(byte[] array, int offset, int count)
        {
            if (array == null)
                throw new ArgumentNullException("array");
            CheckObjectDisposedException();
            if (!m_stream.CanRead)
            {
                throw new NotSupportedException("Cannot read from stream");
            }
            if (offset < 0)
                throw new ArgumentOutOfRangeException("offset", "< 0");
            if (count < 0)
                throw new ArgumentOutOfRangeException("count", "< 0");
            // re-ordered to avoid possible integer overflow
            if (array.Length - offset < count)
                throw new ArgumentException("array.Length - offset < count");

            if (!m_buffer_reading)
            {
                Flush();
                m_buffer_reading = true;
            }

            if (count <= m_buffer_read_ahead - m_buffer_pos)
            {
                Array.Copy(m_buffer, m_buffer_pos, array, offset, count);

                m_buffer_pos += count;
                if (m_buffer_pos == m_buffer_read_ahead)
                {
                    m_buffer_pos = 0;
                    m_buffer_read_ahead = 0;
                }

                return count;
            }

            var ret = m_buffer_read_ahead - m_buffer_pos;
            Array.Copy(m_buffer, m_buffer_pos, array, offset, ret);
            m_buffer_pos = 0;
            m_buffer_read_ahead = 0;
            offset += ret;
            count -= ret;

            if (count >= m_buffer.Length)
            {
                ret += m_stream.Read(array, offset, count);
            }
            else
            {
                m_buffer_read_ahead = m_stream.Read(m_buffer, 0, m_buffer.Length);

                if (count < m_buffer_read_ahead)
                {
                    Array.Copy(m_buffer, 0, array, offset, count);
                    m_buffer_pos = count;
                    ret += count;
                }
                else
                {
                    Array.Copy(m_buffer, 0, array, offset, m_buffer_read_ahead);
                    ret += m_buffer_read_ahead;
                    m_buffer_read_ahead = 0;
                }
            }

            return ret;
        }

        public override void Write(byte[] array, int offset, int count)
        {
            if (array == null)
                throw new ArgumentNullException("array");
            CheckObjectDisposedException();
            if (!m_stream.CanWrite)
            {
                throw new NotSupportedException("Cannot write to stream");
            }
            if (offset < 0)
                throw new ArgumentOutOfRangeException("offset", "< 0");
            if (count < 0)
                throw new ArgumentOutOfRangeException("count", "< 0");
            // avoid possible integer overflow
            if (array.Length - offset < count)
                throw new ArgumentException("array.Length - offset < count");

            if (m_buffer_reading)
            {
                Flush();
                m_buffer_reading = false;
            }

            // reordered to avoid possible integer overflow
            if (m_buffer_pos >= m_buffer.Length - count)
            {
                Flush();
                m_stream.Write(array, offset, count);
            }
            else
            {
                Array.Copy(array, offset, m_buffer, m_buffer_pos, count);
                m_buffer_pos += count;
            }
        }

        private void CheckObjectDisposedException()
        {
            if (disposed)
            {
                throw new ObjectDisposedException("Stream is closed");
            }
        }
    }
}